[Spin labels in the analysis of Ca-ATPase in the sarcoplasmic reticulum of rabbit skeletal muscles in hypercholesteremia].

The method of electron paramagnetic resonance with spin-labeled maleimide was used to study variation of the structure of Ca-ATPase of the sarcoplasmic reticulum (SR) in rabbit skeletal muscles under long-term hypercholesterolemia (HC). The rate of the maleimide spin label binding with Ca-ATPase of the SR was decreased in HC, which correlated with a lesser access of spin-labeled thiol groups for potassium ferricyanide and sodium ascorbate. HC led to a considerable reduction in the lability and to enhancement of hydrophobia of the spin-labeled fragment of the enzyme. It is concluded that the disordered function of the SR Ca-pump is a consequence of structural changes in the Ca-ATPase molecule in HC.